Gadget Freak Case #228: Super LED Flashlight Hits 3,000 Lumens

Fifteen-year-old Gadget Freak John Duffy has put together a powerful LED flashlight. He calls the LED a major advance over Edison's incandescent lighting. "Nowadays we have LEDs that are significantly more powerful and efficient, and they run on low-voltage DC."

Duffy's super LED flashlight runs at almost 30W and 3,000 lumens. By comparison, bright xenon car headlights reach about 1,000 lumens. He says you have to be careful building and using this gadget, because it is powerful enough to blind someone if used up close. He used welding glasses while constructing the flashlight.

John Duffy's super LED flashlight is almost three times as powerful as xenon car headlights.

In the series/parallel arrangment John used (3x3 of 10 W originally, and I have to assume 2x2 of 20W in the parts list), both the current and the voltage divide among the 9 resistors. 1/3 I x 1/3 E = 1/9 P in each resistor. Doesn't matter a whit, if they are all in series, all in parallel, or in groups like this.

It's all a bit overkill, though. Unless I haven't had enough coffee yet this morning, dropping 2.5V at 2.5A is only 6.25 Watts. Still a bit much for a single 1 Ohm/10 Watt resistor, but should be no sweat for a single 1 Ohm/20 Watt, as in the parts list.

It's great to read about this young man "tinkering" with stuff...nice project! John Duffy, keep up the great work, and consider an engineering or science degree, and career!

All too often, interviewing engineering personnel candidates, I found that many young degreed engineers have never worked with/on anything while growing up (or currently). They have not had projects building gadgets, fixing things, or modifying stuff. They say things such as they like cars, but have never attempted any work on cars. I wonder if they can even hammer a nail, or screw-in a screw...use a tool. Installing software and playing video games does not count to me as a project or tinkering.

By age 18, my list of projects and accomplishments was huge, a lot of practical experience...including advanced auto and motorcycle mechanics, and Hot Rodding (modifying to be powerful and fast). Growing up, I helped my dad with numerous house and car repairs, my dad was an engineer (now retired).

I don't mean to argue, but I think you need to re-think that. If I place two 1K, 1-Watt resistors in series, I end up with a 2K, 1-watt resistor. The same holds true for three series 1/3-ohm, 30-watt resistors, as in John's example. It ends up being a 1-ohm, 30-watt resistor.

If John had started with nine 9-ohm, 10-watt resistors, and placed them ALL in parallel, I agree that he would end up with a 1-ohm, 90-watt resistor. That's not what he describes, however.

To aid in your LED lighting research experiments, here's a cool online circuit simulation website called Circuit Lab. Nice way to do paper analysis first and then model it using software. Here's the link below. Enjoy!!!

I shared your Gadget Freak video with a group of DC-AC Electronics students at ITT Tech to get them motivated about Electrical-Electronics Engineering Tech. I wanted to illustrate the importance of doing homework, which you elegantly demonstrated, in the video based on your LED research. Keep the good work!!!

Paralleling three equal 10W resistors will, as you agreed give you a 30W equivalent.

Placing three equal 30W resistors *however achieved* in series will indeed give you a 90W equivalent. If all nine resistors are of the same value, the combination will have the equivalent resistance of a single resistor, with nine times the power rating.

You are correct that three 10-watt resistors in parallel will make a 30-watt resistor that is one-third the resistance. But then adding three of these 30-watt resistors in series will only result in a resistor of the original value, but STILL only capable of dissipating 30 Watts, not 90W as you stated.

John: I am impressed with your results and would like to talk to you about your future. My name is Frank Rudolph and you can reach me on Linked-In under that name. You can reach me on Linked-In or directly at docrudolph@gmail.com, or at rudolph@beaconpower.com. At Beacon Power, our corporate charter focuses on alternative energy and sustainability.

Incidentally, if you don't already have a Linked-In account, you should get one now!! Judging from what I have read here, you have a brilliant career ahead of you, and making contacts with a network of people in the industry should start for you right now! Good job! Keep on thinking of new stuff.

You're clearly well on your way to an elustrious career in electrical engineering. Do take a look at the ol' LM317 (LM117,217,317) voltage regulator datasheet. Somewhere in the back is a constant current regulator circuit that you will find very useful in your line of research. Also, check out Natsemi's (now TI) boost switching regulators. Just add an inductor, a FET, a diode and a bunch of caps to nake a voltage step-up constant current regulator. I just finished a controller design to drive those ebay 100W modules (33V @ 3A) off of 12V power. Keep having fun.

Followers of Design News’ Gadget Freak blogs will have the opportunity next week to take home a wireless remote demo package that can be used to build garage door openers, tire pressure monitors, keyless entry systems, and much more.

The 2015 Gadget Freak of the Year goes to the DDV-IP -- or, a Drink Deliver Vehicle – Inverted Pendulum. The gadget is a two-wheeled self-balancing robot that can deliver cold beverages to thirsty folks on a hot summer day. A wireless RF remote enables manual control of the device beyond the act of self-balancing. All of the features of the DDV-IP result in an effective delivery vehicle while providing entertainment to the users.

Focus on Fundamentals consists of 45-minute on-line classes that cover a host of technologies. You learn without leaving the comfort of your desk. All classes are taught by subject-matter experts and all are archived. So if you can't attend live, attend at your convenience.